JPH0726594B2 - Engine exhaust heat recovery device - Google Patents

Description

The present invention relates to a device for recovering exhaust heat from an engine such as an engine main body or exhaust heat, and even if the liquid recovery rate of the heat recovery liquid fluctuates greatly, The thing which can suppress a change small is provided.

<Prior Art> The basic structure of an exhaust heat recovery system for an engine to which the present invention is applied is, as shown in FIG. 1 or 3, a water jacket 2 of an engine E and an exhaust heat absorbing heat exchanger 3 of an engine E. The exhaust heat absorption channel 4, the hot water channel 5, the heat recovery discharge side water channel 7 of the engine exhaust heat recovery heat exchanger 6, and the cold water channel 8 are connected in series in a serial circulation manner.

As a conventional technique of this type, as shown in US Pat. No. 4,226,214 (see FIG. 4), an engine E and a generator G are used.
In the engine exhaust heat recovery heat exchanger 6, the engine main body heat absorbed in the water jacket 2 and the exhaust heat absorbed in the exhaust heat absorption path 4 are generated in the heat exchanger 6 while the power generator G generates electricity. The heat is dissipated and the exhaust heat of the engine E is recovered from the heat absorption side water passage 15 of the heat exchanger 6.

Reference numeral 50 is a three-way valve for switching that allows the engine E to be warmed up early by short-circuiting the cooling water passage from the hot water passage 5 directly to the cold water passage 8 when the engine E is started.

<Problems to be Solved by the Invention> However, in the above-mentioned conventional technique, the heat recovery hot water discharged from the engine exhaust heat recovery heat exchanger 6 is reduced by reducing the heat recovery amount due to external factors such as seasonal factors and personnel factors. If the flow rate of the heat recovery hot water is largely decreased, the exhaust heat of the engine E is concentrated and absorbed in a small amount of the heat recovery hot water, so that the temperature of the heat recovery hot water may rise rapidly and deviate from the appropriate temperature range to a high temperature. There is

Conversely, when the heat recovery amount is increased and the flow rate of the heat recovery hot water discharged from the engine exhaust heat recovery heat exchanger 6 is changed to a large increase side, the exhaust heat of the engine E becomes a large amount of heat recovery hot water. Since heat is dispersed and absorbed, there is a risk that the temperature of the heat recovery hot water will suddenly drop and fall outside the proper temperature range.

An object of the present invention is to suppress the temperature change of the heat recovery liquid to be small irrespective of whether the rate of change of the flow rate of the heat recovery liquid discharged from the heat exchanger largely fluctuates, positive or negative.

<Means for Solving the Problems> Means for solving the above problems will be described below with reference to the drawings corresponding to the embodiments.

That is, according to the present invention, in the engine exhaust heat recovery device having the basic structure, the heat recovery discharge side water passage 7 of the engine exhaust heat recovery heat exchanger 6 is connected in parallel to the heat dissipation passage 10 of the radiator 1, A variable diversion valve 12 can diverge the heat recovery discharge side water passage 7 and the heat radiation passage 10 from the engine cooling water passage 11 including the cold water passage 8, the water jacket 2, the exhaust heat absorption passage 4, and the hot water passage 5. Connected to the heat exchanger 6 for heat recovery from the engine exhaust heat
15 is provided with a temperature sensor 30 to enable detection of the liquid temperature of the heat recovery liquid passing through the heat recovery side heat absorption side liquid path 15, and the variable flow dividing valve 12 is provided to the temperature sensor 30 via the flow dividing ratio control device 14. In cooperation with controllable control, the diversion rate control device 14 actuates the variable diversion valve 12 according to the temperature detected by the temperature sensor 30 so that the cooling water from the engine cooling water passage 11 to the heat radiation passage 10 and the heat recovery discharge water passage By controlling the diversion rate with the cooling water to 7, it is possible to adjust the liquid temperature of the heat recovery liquid within a predetermined temperature range. The flow rate of the heat recovery liquid passing through the recovery heat absorption side liquid passage 15 can be detected,
The variable flow dividing valve 12 is linked to the flowmeter 35 via the flow dividing rate control device 14 so that the flow dividing rate can be controlled, and the change rate Q of the detected flow rate of the heat recovery liquid of the flowmeter 35 becomes negative,
When the flow rate reduction rate becomes equal to or lower than the lower limit value Q (L) on the heat radiation reduction side, the flow dividing rate control device 14 operates the variable flow dividing valve 12 to the heat radiation increasing side regardless of the temperature detected by the temperature sensor 30. , The radiating side diversion rate of the cooling water from the engine cooling water channel 11 to the radiating channel 10 is increased, and the heat collecting discharge side water channel 7 is provided.
The heat recovery side diversion rate of the cooling water to the flow rate is decreased, and the rate of change Q of the detected flow rate of the heat recovery liquid of the flow meter 35 becomes positive,
When the flow rate increase rate becomes equal to or higher than the heat radiation increasing side upper limit value Q (H), the flow dividing rate control device 14 operates the variable flow dividing valve 12 to the heat radiation reducing side regardless of the temperature detected by the temperature sensor 30. The heat radiating side diversion rate is reduced and the heat recovery side diversion rate is increased.

<Operation> The temperature sensor 30 detects the liquid temperature of the heat recovery liquid passing through the heat recovery heat absorption side liquid passage 15 of the engine exhaust heat recovery heat exchanger 6. The diversion rate control device 14 actuates the variable diversion valve 12 in accordance with the detected temperature to change the diversion rate of the cooling water from the engine cooling water passage 11 to the heat radiation passage 10 and the cooling water to the heat recovery discharge side water passage 7. By controlling, the liquid temperature of the heat recovery liquid in the heat recovery side heat absorption side liquid passage 15 is adjusted within a predetermined temperature range (appropriate temperature range).

On the other hand, (1) the heat absorption side liquid passage 15 of the engine exhaust heat recovery heat exchanger 6
If the amount of heat recovery liquid that passes through is rapidly decreased, that is, if the detected flow rate decrease rate Q of the flowmeter 35 ≤ heat radiation reduction side lower limit value Q (L) (the absolute value of the detected flow rate reduction rate Q is the heat radiation reduction side Lower limit value Q
(When it becomes larger than the absolute value of (L)) Regardless of the temperature detected by the temperature sensor 30, the diversion rate control device 14 operates the variable diversion valve 12 to the heat radiation increasing side, and the engine cooling water passage 11 to the heat radiation passage 10 Since the heat dissipation side diversion rate of the cooling water to the engine increases, the ratio of the engine exhaust heat radiated to the outside of the cooling water circulation system by the radiator 1 increases, and the engine exhaust heat amount itself reaching the engine exhaust heat recovery heat exchanger 6 increases. Reduce.

As a result, even if the amount of the heat recovery liquid passing through the heat recovery side heat absorption side liquid passage 15 sharply decreases, the amount of heat exhausted from the engine, which is the target of the heat recovery corresponding to this, rapidly decreases.

That is, when the amount of the heat recovery liquid passing through the heat recovery heat absorption side liquid passage 15 of the engine exhaust heat recovery heat exchanger 6 decreases, the engine exhaust heat amount reaching the heat exchanger 6 absorbs heat with a small amount of the heat recovery liquid. Therefore, the temperature of the heat recovery liquid rises.

By the way, for example, if it is configured to control the diversion rate of the cooling water from the engine cooling water passage 11 to the heat radiation passage 10 and the cooling water to the heat recovery discharge side water passage 7 only by detecting the temperature with the temperature sensor 30, The reduced heat recovery rate of the temperature sensor is increased by the heat exchange through the heat exchanger 6, and then the temperature sensor
If it does not reach 30, the radiating flow side diversion rate of the cooling water will not be increased according to the temperature rise of the heat recovery liquid.

That is, there is a response delay from the decrease of the amount of the heat recovery liquid passing through the heat recovery heat absorption side liquid path 15 to the increase of the cooling water radiating side diversion rate. For this reason, there is a possibility that the temperature of the heat recovery liquid rises during this response delay and deviates from the proper temperature range.

On the other hand, in the present invention, when the decrease in the amount of the heat recovery liquid passing through the heat recovery endothermic side liquid passage 15 is detected by the flow meter 35, the temperature of the heat recovery liquid is reduced with the decrease in the amount of the heat recovery liquid. Is considered to increase, the heat-dissipation liquid suppresses the temperature rise because the heat-dissipation-side diversion rate of the cooling water is increased and the engine exhaust heat quantity to the heat exchanger 6 is reduced regardless of the temperature detected by the temperature sensor 30. And maintained within the proper temperature range.

(2) Heat absorption side liquid passage 15 of heat exchanger 6 for recovering engine exhaust heat
When the amount of the heat recovery liquid passing through the chamber rapidly increases, that is, when the heat radiation increasing side upper limit value Q (H) ≤ the detected flow rate increase rate Q of the flow meter 35, the diversion rate control device 14 detects the temperature detected by the temperature sensor 30. Irrespective of the above, the variable shunt 12 is operated toward the heat radiation reducing side, and the heat radiation side diversion rate of the cooling water from the engine cooling water passage 11 to the heat radiation passage 10 is reduced, so the engine exhaust heat is dissipated outside the cooling water circulation system by the radiator 1. The rate of heat dissipation is reduced, and the engine heat recovery heat exchanger 6
The amount of heat exhausted from the engine itself reaches

As a result, even if the amount of the heat recovery liquid passing through the heat recovery heat absorption side liquid passage 15 suddenly increases, the engine exhaust heat to be the target of the heat recovery rapidly increases correspondingly.

That is, as in the case of reducing the heat recovery device described above, for example, when the cooling water diversion rate is controlled only by the temperature detection by the temperature sensor 30, the heat recovery liquid amount increases and the cooling water radiates. During the response delay until the side diversion rate decreases, the temperature of the heat recovery liquid may drop and fall out of the proper temperature range.

On the other hand, in the present invention, when the increase in the amount of the heat recovery liquid is detected by the flow meter 35, the temperature of the heat recovery liquid is considered to decrease, and the cooling water radiating side diversion is performed regardless of the temperature detected by the temperature sensor 30. Since the rate is decreased to increase the amount of heat exhausted from the engine to the heat exchanger 6, the temperature of the heat recovery liquid is suppressed from decreasing and is maintained within the proper temperature range.

<Effects of the Invention> When the heat recovery liquid is adjusted within the predetermined temperature range (appropriate temperature range) according to the temperature detected by the temperature sensor, if the flow rate change rate of the heat recovery liquid fluctuates significantly, the engine cooling water channel Since the cooling water from the heat sink to the radiating passage and the cooling water to the discharge side water passage for heat recovery are controlled to a diversion rate that matches the above flow rate fluctuations regardless of the temperature detected by the temperature sensor, heat recovery accompanying the above flow rate fluctuations is controlled. The diversion rate can be quickly controlled without causing a response delay with respect to the temperature change of the liquid. As a result, the temperature change of the heat recovery liquid can be suppressed to be small and the temperature of the heat recovery liquid can be reliably maintained within the appropriate temperature range. <Example> Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a system principle diagram of a cogeneration engine generator, and FIG. 2 is a relationship diagram of a flow rate change rate of heat recovery water and a radiator-side cooling water flow rate in the cogeneration engine generator. The vertical gas engine E and the generator G are interlockingly connected in the front-rear direction to generate electric power, and at the same time, to recover the engine exhaust heat of the heat of the engine body and the exhaust heat.

The water jacket 2 is formed in the cylinder block and cylinder head of the gas engine E, and the exhaust heat absorbing heat exchanger 3 and the muffler 20 are attached to the exhaust passage 21 of the engine E in order.

Further, a radiator 1 is attached to the engine E so that engine exhaust heat can be radiated to the outside of the cooling water circulation system, and an engine exhaust heat recovery heat exchanger 6 is attached to recover the heat of the heat exchanger 6. The engine exhaust heat is released in the heat release side water channel 7, and the exhaust heat is recovered in the heat absorbing side water channel 15
The hot water supplied from the heat absorption side water passage 15 is stored in the hot water tank 23 and used for hot water supply.

Incidentally, reference numeral 24 is a control device, which controls the cooling fan 25 of the radiator 1, a circulation pump 22, which will be described later, a pressure reducing valve in the gas fuel introduction path, and the like.

The water jacket 2 has a heat exchanger 3 for absorbing exhaust heat.
Exhaust heat absorption path 4 and the cooling water that has undergone heat exchange
The hot water passage 5 derived from the cooling water passage 8, the cold water passage 8 for introducing the cooling water before heat exchange into the engine E, and the circulation pump 22 are connected in series and connected in series, and between the hot water passage 5 and the cold water passage 8, The heat dissipation path 10 passing through the radiator 1 and the heat recovery discharge water path 7 of the engine exhaust heat recovery heat exchanger 6 are connected in parallel.

However, reference numeral 26 is a thermostat valve, which is arranged at a branch inlet portion of a bypass passage 27 branched from the hot water passage 5 to the cold water passage 8 in a short-circuited manner. The cooling water exiting E is circulated in a short circuit from the hot water passage 5 to the cold water passage 8 to minimize the amount of heat radiation,
It is structured so that it can be warmed up early.

On the other hand, the heat radiating passage 10 and the heat recovery discharge side water passage 7 are bifurcated from the hot water passage 5, and a variable shunt valve 12 composed of a three-way valve is provided at the bifurcated portion of the hot water passage 5. 6
A light gauge 35 is attached to the heat absorption side water passage 15 of the
In cooperation with the variable diversion valve 12 via the diversion rate control device 14 so that the diversion rate can be controlled, even if the amount of hot water passing through the heat absorption side water passage 15 largely changes, the hot water temperature is kept within a certain range. It is configured to be able to hold.

That is, of the change rate Q of the hot water supply amount detected by the flow meter 35,
Heat dissipation increasing side upper limit value Q (H) as a positive direction allowable upper limit value (that is, increase rate allowable upper limit value), and heat dissipation decreasing side as a negative direction allowable lower limit value (that is, decrease rate allowable lower limit value) The lower limit value Q (L) is set in the diversion rate control device 14, respectively.

Then, the variable shunt valve 12 is controlled as in the following (1) to (3) according to the level of the detection change rate Q of the hot water supply amount by the temperature sensor 35 with respect to the allowable lower limit value Q (H) and the allowable lower limit value Q (L). Then, the hot water passage 5 → the heat radiation passage 10 The hot water passage 5 → The heat distribution discharge side water passage 7 of the heat exchanger 6 is changed in the flow dividing ratio to the two passages to change the ratio of heat radiation and heat collection. To be done.

However, a temperature sensor 30 is attached to the heat absorption side water passage 15 of the engine exhaust heat recovery heat exchanger 6, and when the rate of change in the flow rate of the hot water supply remains within the normal range, the temperature sensor 30 It is configured to control the variable shunt valve 12 based on the hot water temperature information from the hot water supply, and only when the rate of change in the flow rate of the hot water is abnormally large.
The variable diversion valve 12 is configured to be interrupted based on the flow rate change rate information from the flow meter 35.

(1) When the detected flow rate change rate Q ≦ heat radiation decrease lower limit Q (L) (that is, when the flow rate decrease rate of the hot water from the heat exchanger 6 becomes abnormally large) As shown in FIG. Due to the action of the variable flow dividing valve 12 in response to the instruction of the flow dividing rate control device 14, as the detected flow rate decrease rate Q increases, the heat radiating side flow dividing rate of the cooling water to the heat radiating path 10 is increased from the initial value a% to recover the heat. The heat recovery side diversion rate to the discharge side water channel 15 is reduced.

Therefore, if the rate of decrease in the amount of hot water supplied increases,
Since the flow rate of the cooling water to the heat radiation path 10 increases and the heat radiation rate increases, the rate of the engine exhaust heat reaching the heat exchanger 6 decreases, so a small amount of hot water supply is a small amount of engine exhaust heat commensurate with the amount. The heat of water is absorbed and the rise in the temperature of the hot water supply is quickly suppressed.

(2) When the upper limit value Q (H) on the heat radiation increasing side ≦ the detected flow rate change rate Q (that is, when the flow rate increase rate of the hot water from the heat exchanger 6 becomes abnormally large), as shown in FIG. As the detected flow rate increase rate Q increases due to the action of the variable flow dividing valve 12 in response to the command from the flow dividing rate control device 14, the flow radiating side flow dividing rate of the cooling water to the heat radiating path 10 is decreased from the initial value a%, and The heat recovery side diversion rate to the recovery discharge side water channel 15 is increased.

Therefore, when the rate of increase in the amount of hot water supplied increases, the warm water channel 5 →
The diversion rate of the cooling water to the heat radiation path 10 is reduced, the heat radiation rate is reduced, and the rate of engine exhaust heat reaching the heat exchanger 6 is increased. Therefore, a large amount of hot water is equivalent to the amount of engine exhaust heat. The heat of water is absorbed and the decrease in the hot water supply water temperature is quickly suppressed.

(3) Lower limit value Q (L) for heat radiation reduction side <Detected flow rate change rate Q <
In the case of the heat radiation increasing side upper limit value Q (H) (when the change rate Q of the hot water supply flow is within the normal range) As described above, the interrupt control based on the information of the flow rate change rate Q from the flow meter 35 is canceled. The variable shunt valve 12 is controlled based on the hot water supply temperature from the temperature sensor 30.

This is because even if the amount of hot water supply changes gently or does not change, the load on the engine generator itself changes and the engine exhaust heat changes, and as a result, the temperature of the hot water supply rises and falls. This is because it is necessary to keep the change in water temperature small.

That is, the heat dissipation control temperature range is set by the diversion rate control device 14, and the lower limit of this temperature range is set to the heat dissipation start temperature T.
₂ (L), the upper limit of which is the temperature T at which the heat dissipation rate becomes 100%
₂ (H), the temperature sensor 30 for this temperature range A
The variable shunt valve 12 is controlled as shown in (a) to (c) below according to the level of the detected hot water supply temperature T ₂ of the hot water supply path 5 → heat radiation path 10 hot water path 5 → for heat recovery of the heat exchanger 6. It is configured to change the diversion rate to the two channels of the discharge side water channel 7 to change the ratio of heat radiation and heat recovery.

However, as a matter of course, T ₂ (L) <T ₂ (H), and in practice, it is good to keep the hot water supply water temperature from the heat recovery side end channel 15 around 80 ° C. Centering at ± 3 ° C, T ₂ (L) is set to 77 ° C and T ₂ (H) is set to 83 ° C.

(A) When the detected temperature T ₂ <heat radiation start temperature T ₂ (L) (that is, when the hot water supply temperature is abnormally decreased) The variable flow dividing valve 12 controls the variable flow dividing valve 12 so that the flow dividing rate to the heat radiating path 10 is small. At 0%, the diversion rate to the heat recovery discharge side water channel 7 is 10%.
The engine cooling water, which has been controlled to be 0% and has absorbed the engine exhaust heat, is cooled by the hot water passage 5.
To the heat release side water passage 7 of the heat exchanger 6 through the variable flow dividing valve 12, and the engine exhaust heat accumulated in the cooling water is recovered in the heat recovery endothermic water passage 15.

Then, the cooling water after the heat is recovered by the heat exchanger 6 is returned to the water jacket 2 of the engine E by the circulation pump 22 through the cold water passage 8 and absorbs the exhaust heat of the engine E again.

(B) When heat radiation start temperature T ₂ (L) ≤ detection temperature T ₂ ≤ total discharge temperature T ₂ (H) (that is, when the hot water temperature is in the normal temperature range) 12 is shunt controlled as follows.

As the detected temperature T ₂ increases, the heat radiation side diversion rate to the heat radiation path 10 increases and the heat recovery side diversion rate to the heat recovery discharge side water channel 15 decreases.

As the detected temperature T ₂ becomes lower, the heat radiation side diversion rate to the heat radiation path 10 is decreased, and the heat recovery side diversion rate to the heat recovery discharge side water channel 15 is increased.

Therefore, as the detected temperature T ₂ increases, the warm water channel 5 → the heat radiation channel
The split ratio of the cooling water to 10 is increased, the heat dissipation efficiency of the cooling water is increased, and the hot water temperature of the hot water passage 5 is rapidly lowered.

As a result, the temperature of the hot water supplied from the heat recovery side heat absorption side water passage 15 of the heat exchanger 6 is also rapidly lowered and adjusted to an appropriate temperature.

On the contrary, as the detected temperature T ₂ decreases, the proportion of the cooling water diverted from the hot water passage 5 to the heat recovery discharge side water passage 7 increases, and the heat dissipation efficiency of the cooling water decreases, and the hot water temperature of the hot water passage 5 decreases. Rises quickly.

As a result, the temperature of the hot water supplied from the heat recovery side heat absorption side water passage 15 of the heat exchanger 6 also rises rapidly and is adjusted to an appropriate temperature.

(C) When the total discharge temperature T ₂ (H) <the detection temperature T ₂ (that is, when the hot water temperature rises abnormally) The variable flow dividing valve 12 causes the variable flow dividing valve 12 to change the flow dividing rate to the radiating furnace 10. At 100%, the diversion rate to the heat recovery discharge side water passage 7 is controlled to be 0%, and the cooling water flowing out from the engine E all flows into the heat radiation passage 10 from the hot water passage 5 through the variable diversion valve 12. Quickly dissipate engine exhaust heat stored in cooling water to the outside of the system.

As a result, the cooling water temperature of the heat recovery discharge side water channel 7 decreases,
The hot water supply water temperature of the heat absorption side water passage 15 from which heat is to be recovered also decreases.

On the other hand, when the temperature sensor 13 is attached to the hot water passage 5 and the temperature sensor 13 is linked to the variable diversion valve 12 via the diversion rate control device 14, when the hot water passing through the hot water passage 5 rises abnormally. The flow rate change rate Q information from the flow meter 35 and the hot water supply water temperature T ₂ information from the temperature sensor 30 are given the highest priority, and the hot drainage temperature T ₁ information from the temperature sensor 13 is given to the diversion rate control device 14. Interrupt control of the variable shunt valve 12 via
The engine E is configured to prevent overheating.

That is, the upper limit temperature T ₁ (H) is set in the diversion rate control device 14,
The hot drainage temperature T ₁ of the engine E detected by the temperature sensor 13 is
The following controls (a) to (b) are performed depending on the level of the upper limit temperature T ₁ (H).

(A) When the detected temperature T ₁ <the upper limit temperature T ₁ (H) (that is, when the engine hot drainage is in the normal temperature range), it is variable based on the information of the hot water supply detection temperature T ₂ from the temperature sensor 30. The diversion rate control of the diversion valve 12 is the above (a) to (c).
Is performed by the diversion rate controller 14.

(B) When the upper limit temperature T ₁ (H) is equal to or lower than the detection temperature T ₁ (that is, when the engine hot drainage is abnormally increased) As described above, the information from the temperature sensor 13 is the above flow meter.
35 works by prioritizing the information from the temperature sensor 30 and the heat radiation path.
Assuming that the flow rate of the cooling water flowing through 10 is 100%, the heat exchanger 6
Of the heat recovery discharge side water passage 7 is controlled so that the flow dividing ratio is 0%, and all the hot water flowing through the hot water passage 5 is caused to flow to the radiator 1 side, thereby the cooling water circulation system. The rate of heat radiation to the outside of the system is maximized, and the warm waste water from the engine E is cooled early to prevent the engine E from overheating.

In this control, in order to avoid hunting, the heat radiating side diversion rate is kept at 100% until the temperature of the hot water drops to a temperature far below the upper limit temperature T ₁ (H).

Further, the temperature sensor 13 is a cooling water channel including a hot water channel 5, a cold water channel 8, a water jacket 2 and an exhaust heat absorption channel 4.
Although it may be provided in any of 11, it is preferable to measure the hot water temperature of the hot water passage 5 in order to quickly prevent the engine E from overheating.

As described above, the present invention provides a flow meter attached to the heat absorption side liquid passage of the engine exhaust heat recovery heat exchanger, and controls when the flow rate change rate of the heat recovery liquid that lowers the flow passage greatly changes. It is characterized in that the cooling water that has absorbed the engine exhaust heat is distributed to the heat radiation channel of the radiator and the heat recovery channel of the heat exchanger at a predetermined diversion rate by the action of the variable flow diversion valve linked to the temperature sensor via the device. Therefore, the engine E is not limited to the engine generator, but other engine working machines such as an engine compressor and an engine welder,
Alternatively, the engine alone can be used.

The variable flow dividing valve 12 is not limited to the three-way valve as in the above-described embodiment, and as shown in FIG. 3, for example, a common two-way valve is provided for the heat radiation passage 10 branched from the warm water passage 5 and the heat recovery discharge side water passage 7. Directional metering valves 12a are attached respectively, and these are combined into one flow rate controller 1
It can be configured to work with 4.

Further, the radiator 1 is not limited to the radiator and may be a condenser or a hopper.

The heat recovery liquid flowing through the water path on the heat absorption side of the engine exhaust heat recovery heat exchanger is not limited to water as in the above embodiment, and may be oil or the like.

[Brief description of drawings]

FIG. 1 is a principle system diagram of an engine exhaust heat recovery system showing an embodiment of the present invention, FIG. 2 is a relationship diagram of a flow rate change rate of heat recovery liquid and a diversion rate to a heat radiation path, and FIG. 3 is a variable diversion. FIG. 4 is a system diagram of an essential part showing another embodiment of the valve, and FIG. 4 is a view corresponding to FIG. 1 showing a conventional technique. 1 ... Radiator, 2 ... Water jacket, 3 ... Exhaust heat absorption heat exchanger, 4 ... Exhaust heat absorption path, 5 ... Warm water path, 6 ... Engine exhaust heat recovery heat exchanger, 7 ...... 6 Discharge side waterway for heat recovery, 8 …… Cold waterway, 10 …… Radiation path, 12
...... Variable flow divider valve, 14 ...... Diversion rate control device, 15 ...... 6 Heat absorption side fluid path for heat recovery, 30 ...... Temperature sensor, 35 ...... Flowmeter,
E …… Engine, Q …… Detected flow rate change rate, Q (L) ……
Heat radiation decrease side lower limit value, Q (H) ... Heat radiation increase side upper limit value.

Claims (1)

[Claims] 1. A water jacket (2) of an engine (E), an exhaust heat absorption path (4), a hot water path (5), and an engine exhaust heat recovery heat exchanger of an exhaust heat absorption heat exchanger (3). Discharge side waterway (7) and cold waterway (8) for heat recovery of (6)
In an exhaust heat recovery system for an engine, which is configured by sequentially connecting in series circulation manner, the heat of the radiator (1) is radiated to the heat recovery discharge side water channel (7) of the engine exhaust heat recovery heat exchanger (6). The channels (10) are connected in parallel to each other to the engine cooling water channel (11) including the cooling channel (8), the water jacket (2), the exhaust heat absorption channel (4), and the hot water channel (5). On the other hand, the heat recovery discharge side water channel (7) and the heat radiation channel (10) are variably connected by a variable flow diverter valve (12), and the heat of the engine exhaust heat recovery heat exchanger (6) is A temperature sensor (30) is provided in the heat recovery side liquid passage (15) so that the liquid temperature of the heat recovery liquid passing through the heat recovery side liquid passage (15) can be detected, and the temperature sensor (30). Shunt controller (1
4) via the variable diversion valve (12) so that the diversion rate can be controlled, and the diversion rate control device (14) controls the variable diversion valve (12) according to the temperature detected by the temperature sensor (30). To activate
By controlling the diversion rate of the cooling water from the engine cooling water channel (11) to the heat radiation channel (10) and the cooling water to the heat recovery discharge side channel (7), the liquid temperature of the heat recovery liquid is controlled. A heat recovery liquid configured to be adjustable within a predetermined temperature range, provided with a flow meter (35) in the heat recovery endothermic side liquid passage (15), and passing through the heat recovery endothermic side liquid passage (15). Of the heat recovery liquid of the flow meter (35) by linking the variable flow dividing valve (12) to the flow meter (35) via the flow dividing rate control device (14) so that the flow rate of the flow meter (35) can be detected. When the rate of change Q in the detected flow rate of becomes negative and the rate of decrease in the flow rate becomes equal to or lower than the lower limit value Q (L) on the heat radiation reduction side, the diversion rate control device (14) operates the temperature sensor (30). Irrespective of the detected temperature of the engine, the variable flow diverter valve (12) is actuated to the heat radiation increasing side to cool the engine cooling water passage (11) to the heat radiation passage (10). The heat recovery side diversion rate of the heat recovery side is increased and the heat recovery side diversion rate of the cooling water to the heat recovery discharge side water channel (7) is decreased to change the rate of change of the detected flow rate of the heat recovery liquid of the flow meter (35). When Q becomes positive and the flow rate increase rate becomes equal to or higher than the heat radiation increase side upper limit value Q (H), the diversion rate control device (14) regardless of the temperature detected by the temperature sensor (30). An exhaust heat recovery device for an engine, characterized in that the variable flow diverter valve (12) is operated toward the heat radiation reducing side to reduce the heat radiating side diversion rate and increase the heat recovery side diversion rate. .